Eric Jensen, 37, and Ryan Jensen, 33, are fourth generation family farmers at Jensen Farms. The brothers turned themselves in to federal marshals and pleaded not guilty to six misdemeanor counts of introducing adulterated food into the food supply.

The listeria outbreak was the deadliest foodborne illness outbreak in 25 years.

Prosecutors said the federal Food and Drug Administration and the Centers for Disease Control and Prevention determined the cantaloupe was contaminated in the Jensens' packing facility.

The FDA said the packing facility had pools of dirty water on the floor, and their equipment was corroded and hard to clean. The Jensens said they recently bought the equipment used.

The brothers claim the changes they made prior to the outbreak was meant to make the food safer, but FDA inspectors say their sorter was meant for potatoes and allowed pooled water to contaminate the melons.

Prosecutors can bring misdemeanor charges whether or not the farmer knew about contamination, but rarely do so. U.S. Attorney spokesman Jeff Dorschner said the Jensen case stood out because of "the magnitude of the number of people who were hospitalized and who died, and it involved 28 of the 50 states."

"I'm glad they were charged. I don't think they did anything on purpose, but I think they had very sloppy farming practices," said Jennifer Exley, whose father was sickened by a contaminated cantaloupe and died in July.

The brothers declined to comment, but their attorneys emphasize they have cooperated through every step of the investigation.

"The charges against Eric and Ryan Jensen do not imply that they knew, or even should have known, that the cantaloupes had been contaminated," said a statement issued by their lawyer. "As they were from the first day of this tragedy, the Jensens remain shocked, saddened, and in prayerful remembrance of the victims and their families."

The federal charges each carry up to one year in prison and a $250,000 fine. A trial date was set for Dec. 2.

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